anaerobic digestion of food waste ss 2013...michael chesshire university of southampton &...
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Jyväskylä Summer School 2013
Anaerobic Digestion
of Food Waste
Michael Chesshire
University of Southampton
&
Evergreen Gas Ltd
Jyväskylä Summer School 2013
Anaerobic digestion - a natural biological process
Biomass
Biofertiliser 40oC
Biogas
Jyväskylä Summer School 2013
Farm
Food
Factory
Abattoir
Food
Retail
Home
Biogas
Plant
Food Waste Chain
S.R.M
Product
Jyväskylä Summer School 2013
UK Context
• Government estimates that each UK household
produces about 250kg of food waste per year,
representing one third of food purchased.
• In total households produce 7 million tonnes of food
waste per year.
• There is a further 10 million tonnes from commercial
catering and from food processing.
• This food waste must be diverted from landfill, and has
the potential for the production of renewable energy
through AD.
Jyväskylä Summer School 2013
Food Waste
R&D Projects
Jyväskylä Summer School 2013
Anaerobic digester for café-bar – 1996-1998
Jyväskylä Summer School 2013
Results
• The anaerobic digestion of food waste worked.
• It was fun.
Jyväskylä Summer School 2013
Demonstration food waste AD for 1000 households – 1999-2001
Jyväskylä Summer School 2013
Results
• Weekly collection.
• 1000 households.
• Food waste – 3.5kg/household/week.
• Digester capacity – 40m3
• Digester temperature – 37oC
• OLR – 3.0kgODM.m-3.d-1.
• BMP – 350m3.tonneODM-1.
• Biogas – 140m3.tonne-1(wet waste).
Jyväskylä Summer School 2013
Mesophilic/thermophilic research trials – 2001-2003
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Food waste preparation
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Operation
• 58 week trial.
• Mesophilic temperature – 37oC.
• Thermophilic temperature – 56oC.
• Digester capacity – 1.5m3 each.
• Digester feed – 4 times per day.
Jyväskylä Summer School 2013
Results (Mesophilic)
• Mean HRT - 31.5 days; OLR - 4.1 kgODM.m-3.d-1.
• Biogas - 4.4 m3.d-1; CH4- 59%.
• Digestate - 5.5%DM, 75% ODM.
• Maximum VFA - 27,400 mg.l-1 (after 35 weeks).
• Ammonia - 5200 mg.l-1.
• pH - 7.3 to 7.7.
• After 35 weeks some of the digestate recycle was
replaced with water to reduce the level of VFA and
ammonia.
Jyväskylä Summer School 2013
Results (Thermophilic)
• Irregular loading because of instability.
• VFA - > 40,000 mg.l-1 (week 25).
• pH – down to 6.8.
• High VFA and low pH required a reduction in loading but
maintaining the HRT (≈30days) by mixing with water.
• Ammonia - 5050 mg.l-1, but reduced to 3600 mg.l-1
when water was added.
Jyväskylä Summer School 2013
Results (Pathogens)
• Log reduction (Mesophilic) – 1.5 to 3.0.
• Log reduction (Thermophilic) – 4.0 to 5.0.
• Pasteurisation (70oC for 1 hour after AD) eradicated
e.coli, faecal streptococci.
Jyväskylä Summer School 2013
Ludlow food waste digester
Jyväskylä Summer School 2013
Ludlow Food Waste Digester
• Partnership between Greenfinch & South Shropshire
District Council.
• Constructed June 2005 to February 2006.
• Commissioned in March to July 2006.
• Decommissioned in September 2012.
• Recycled 4000tpa of kitchen waste.
• Operated by community company.
Jyväskylä Summer School 2013
Jyväskylä Summer School 2013
Environment
Community
AD of
Food Waste
Economy
Jyväskylä Summer School 2013
Kitchen caddy, corn starch bags & kerbside bin
Jyväskylä Summer School 2013
Kerbside bins ready for collection in Ludlow
Jyväskylä Summer School 2013
Ludlow biodigester site before construction
Jyväskylä Summer School 2013
Ludlow biodigester under construction
Jyväskylä Summer School 2013
Food waste delivery
Jyväskylä Summer School 2013
Jyväskylä Summer School 2013
Food waste in reception hall
Jyväskylä Summer School 2013
Shredded food waste
Jyväskylä Summer School 2013
Buffer Tank
Primary
Digester
Biogas
Storage
Secondary
Digester
Process tanks
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CHP & boiler
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Electric collection vehicle
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Liquid biofertiliser
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Solid biofertiliser
Jyväskylä Summer School 2013
Results
• Plant operational for 6 years.
• Initial feedstock garden + food waste.
• Changed to food waste only after 1 year.
• Instability after 2 years operation on food waste only.
• Micronutrients added from 2009.
• After addition of micronutrients:-
• VFA reduced from >30000 mg.l-1 to <1000.
• BMP – increased from 380 to 420 m3.tonneODM-1.
• OLR increased to 3.2kgODM.m-3.d-1.
Jyväskylä Summer School 2013
Co-digestion of pig slurry & food waste in Bedfordshire
Jyväskylä Summer School 2013
45,000 tonnes per year food waste AD plant in Northamptonshire
Jyväskylä Summer School 2013
Co-digestion of food waste with cattle & pig manure in Shropshire
Jyväskylä Summer School 2013
10,000 tonnes per year potato digester in Lincolnshire
Jyväskylä Summer School 2013
300 tonne per year community AD plant
Jyväskylä Summer School 2013
Household biogas plant in India
Jyväskylä Summer School 2013
Thank You